Usefulness of a new serological test (Bio-Rad) to diagnose Helicobacter pylori-associated gastritis.

A semiquantitative serological test (G.A.P. test; Bio-Rad) to diagnose Helicobacter (Campylobacter) pylori-associated gastritis has recently become commercially available. This test was evaluated with sera from 72 dyspeptic patients with known H. pylori status. When the instructions provided by the manufacturer were applied strictly, the sensitivity of the test was only 32.7%. With a slight modification of the instructions, the performance characteristics were still unsatisfactory (specificity, 43.5%). When a new cutoff value was determined by a receiver operating curve, the quality of the test (positive predictive value, 95.6%; negative predictive value, 77.8%) was slightly lower than that of a noncommercial enzyme-linked immunosorbent assay (positive predictive value, 95.7%; negative predictive value, 84.0%). It is concluded that the Bio-Rad G.A.P. test has low diagnostic yield, and it is stressed that commercial tests should be evaluated extensively before being applied in daily practice.